In the case of internal combustion engines, it is known to replace the conventional valve mechanism having camshafts by an electrohydraulic valve actuation. In such an electrohydraulic valve actuation, the gas-exchange valves are assigned solenoid valves, which control the inflow and outflow of a pressurized fluid—an hydraulic oil—into the working chamber of an hydraulic working cylinder. The position of the corresponding gas-exchange valve is modified via the charge of the working chamber of the hydraulic working cylinder.
The advantage of such an electrohydraulic valve timing is that the individual gas-exchange valves of the internal combustion engines may be actuated independently of each other. This provides great variability of the opening and closing instants of the gas-exchange valves. The variability is given both among the gas-exchange valves of different combustion chambers and also among the gas-exchange valves of an individual combustion chamber. By appropriate coordination of the actuation of the solenoid valves, for instance, the valve actuation of two gas-exchange valves having the same function, i.e., two intake valves or two discharge valves, may be synchronized and any existing component tolerances or system-intrinsic deviations be compensated in synchronism.
It is thus known from electrohydraulic valve actuations to ascertain a trigger signal for each individual solenoid valve in a control device, in time-synchronism with the crankshaft motion and possibly as a function of the driving state of the vehicle, the operating states of the internal combustion engine and also as a function of driver inputs. This signal is transmitted to an output stage via an appropriate trigger line. In response to the actuation signal, the corresponding solenoid valve will then be triggered by means of the output stage.
This assumes that a separate control line between the control device and the output stage is provided for each solenoid valve, which causes high cabling expenditure and requires correspondingly higher computing power in the control device. Each actuating signal of the control device must be ascertained and generated in synchronism with the crankshaft.